1. Field of the Invention
The present invention relates to a temporary adhesive composition and a method for manufacturing a thin wafer using this.
2. Description of the Related Art
Three-dimensional semiconductor packaging has been required for realizing further high integration and capacity enlargement. Three-dimensional semiconductor packaging technology means semiconductor fabrication technology for reducing a thickness of one semiconductor chip and laminating many layers while achieving wire connection by using through-silicon vias (TSVs). To realize this technology, there is required an electrode forming step of reducing a thickness of a substrate having a semiconductor circuit formed thereon by backgrinding and forming electrodes and others including TSVs on a back side. At a conventional backgrinding step for a silicon substrate before the electrode forming step, a protection tape is applied to the opposite side of a surface to be ground, and wafer damage in grinding is avoided. However, since this tape uses an organic resin film as a base material, it has flexibility but, on the other hand, it has insufficient strength or heat resistance, and hence it is not suitable when carrying out a wiring layer forming process on a back side.
Therefore, there has been suggested a system that can sufficiently cope with the backgrinding step or the back side electrode forming step by bonding a semiconductor substrate to a support substrate made of, e.g., silicon or glass through an adhesive. At this time, the adhesive when bonding both the substrates is important. This adhesive requires adhesiveness that enables boding the substrates without gaps and sufficient durability that enables coping with subsequent processes. Further, it is important to enable readily delaminating a thin wafer from the support substrate. As described above, since delamination is performed at the end, this adhesive will be referred to as a temporary adhesive.
As a known temporary adhesive and its delamination method, there have been suggested technology for irradiating an adhesive containing a light-absorptive material with light having high intensity, decomposing an adhesive layer, and thereby delaminating the adhesive layer from a support substrate (Patent Document 1) and technology for using a hydrocarbon based hot-melt compound as an adhesive and performing bonding/delamination in a heated and molten state (Patent Document 2). However, the former requires an expensive apparatus such as a laser, and it has a problem that a processing time per substrate is prolonged, for example. Furthermore, the latter is convenient since control is effected by heating alone, but thermal stability is insufficient at a high temperature exceeding 200° C., and a process application range is narrow.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-064040
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-328104
Patent Document 3: U.S. Patent No. 7541264